Since vinylidene fluoride-based resin has excellent weather resistance, heat resistance, chemical resistance, and electrical characteristics and can be easily formed, the vinylidene fluoride-based resin is used for many applications.
Among many applications, for example, when the vinylidene fluoride-based resin is used for a solar cell film, a film for automobile interior decoration, and a greenhouse film for agriculture, high transparency has also been required as well as the above-described characteristics.
To increase the transparency of a film obtained from the vinylidene fluoride-based resin, for example, a method of lowering degree of crystallinity by copolymerization of vinylidene fluoride and hexafluoropropylene to increase film transparency is known. However, to increase the transparency, it is required that the content of a copolymerization component unit in a copolymer is comparatively high. Accordingly, the crystalline melting point of the copolymer becomes lower than the crystalline melting point of a vinylidene fluoride homopolymer. This causes a problem of lowering heat resistance.
As a film excellent in transparency using vinylidene fluoride-based resin, Patent Literature 1 proposes a vinylidene fluoride-based film, which is obtained using a composition including 50 to 99.9 parts by weight of vinylidene fluoride-based resin (D) and 0.1 to 50 parts by weight of methacrylic-based resin composition (C). However, the film with excellent transparency disclosed in PLT 1 is a film where a vinylidene fluoride-based resin film with the thickness of approximately several μm is laminated on a base resin layer that is obtained from a methacrylic-based resin composition (C). In contrast, if a vinylidene fluoride-based resin film with the thickness of approximately several tens to 100 μm is laminated, the transparency of the obtained laminated film is insufficient.
Furthermore, Patent Literature 2 proposes a film that includes polyvinylidene fluoride resin (A) and polymethacrylic resin (B) and is stretched under a specific condition. However, the film disclosed in PLT 2 does not have sufficient transparency when the film is not stretched.
In addition, Patent Literature 3 discloses a stretch film including polyvinylidene fluoride and polymethylmethacrylate with the thickness of 130 μm. However, this stretch film does not have sufficient heat resistance.